During the course of the HIV/AIDS epidemic there has been one constant - ten percent of all new cases occur in adults over the age of 50. In spite of this, the vast majority of all HIV/AIDS research has focused or individuals younger than 50. With the increasing survival of AIDS patients, and the unrelenting rate of new infectiodcases, the number of AIDS patients over 50 years of age is growing. Our lack of understanding about how age and HIV/AIDS interact is becoming increasingly problematic, no more so than in the area of the neurocognitive manifestations of AIDS, since age is itself an important predictor of neurocognitive syndromes- In spite of the known links between age and various neuropsychiatric disorders - including dementia - it has only been recently that much attention has been paid to the possible interactions between HIV/AIDS and aging and neuropsychiatric presentation. The purpose of this study is to compare and contrast neuropsychological deficits, including brain structural and functional abnormalities associated with HIV/AIDS as a function of chronological age. In particular, we will characterize the neuroimaging and neuropsychological defects in older individuals with AIDS focusing on two distinct neuropathologies that can lead to impairment - one via mesial temporal dysfunction (aging), and the other via basal ganglia dysfunction (AIDS). By carefully characterizing the neuropsychological deficits (including those identified using brain imaging technology) we will be better able to understand the interactive effects of agingand HIVIAIDS.